Abstract: A method of classifying a human subject having adolescent idiopathic scoliosis (AIS) comprising: providing a cell sample isolated from the subject; detecting an impairment in melatonin-signaling pathway in the sample in the presence and in the absence of a known melatonin-signaling pathway agonist, whereby the results of the detecting step enables the classification of the subject having AIS in one AIS subgroup; and a method of screening for a compound useful in the treatment of a disease characterized by a dysfunctional melatonin-signaling pathway, said method comprising the steps of contacting a candidate compound with at least one cell expressing at least one melatonin-signaling pathway impairment, wherein the candidate compound is selected if said melatonin-signaling pathway impairment is reduced in the presence of the candidate compound as compared to that in the absence thereof.